title: The prevalence, clinical features and association of HLA-B27 in sacroiliitis associated with established Crohn's disease.
abstract: BACKGROUND
  Sacroiliitis is a recognized complication of Crohn's disease and may occur distinct from progressive ankylosing spondylitis (AS).
  
  
  OBJECTIVE
  To estimate prospectively the prevalence of sacroiliitis in patients with established Crohn's disease, to characterize the clinical features and to correlate these with the presence of HLA-B27.
  
  
  METHODS
  All Crohn's disease patients under active follow-up of between 5 and 12 years duration were invited to participate. Patients underwent a clinical evaluation including symptom questionnaire, rheumatological examination and underwent HLA genotyping. Patients then underwent magnetic resonance imaging (MRI) of the sacroiliac joints. The clinical and radiological factors were correlated with HLA-B27 status.
  
  
  RESULTS
  56 patients underwent initial assessment and 44 had MRI scans. Seventeen of 44 (39%) patients had MRI evidence of sacroiliitis, of whom 5 fulfilled the criteria for AS. Symptoms of low back pain were elicited in a majority of these patients--11/17 (65%) compared to 3 of 27 (11%) patients with normal scans (P = 0.003). There were no differences in functional indices with the exception of patients with AS. HLA-B27 was present in seven patients, and all seven had MRI evidence of sacroiliitis, five had AS.
  
  
  CONCLUSIONS
  Sacroiliitis is common in patients with established Crohn's disease and in the majority of cases, patients have symptoms of inflammatory low back pain if questioned carefully. HLA-B27 is not associated with isolated sacroiliitis, but is associated with AS. However, possession of HLA-B27 appears to convey a very high risk of developing axial inflammation in Crohn's disease.
authors.affiliation: GI Unit, St Mary's Hospital, and Imperial College London, UK. tim.orchard@imperial.nhs.uk
authors.forename: T R
authors.initials: TR
authors.lastname: Orchard
authors.forename: H
authors.initials: H
authors.lastname: Holt
authors.forename: L
authors.initials: L
authors.lastname: Bradbury
authors.forename: J
authors.initials: J
authors.lastname: Hammersma
authors.forename: E
authors.initials: E
authors.lastname: McNally
authors.forename: D P
authors.initials: DP
authors.lastname: Jewell
authors.forename: B P
authors.initials: BP
authors.lastname: Wordsworth
mesh_terms: D000328:Adult; D003424:Crohn Disease / Q000150:complications* / Q000276:immunology / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D015796:HLA-B27 Antigen / Q000276:immunology; D006801:Humans; D017116:Low Back Pain / Q000209:etiology* / Q000276:immunology / Q000503:physiopathology; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D012446:Sacroiliac Joint; D058566:Sacroiliitis / Q000209:etiology* / Q000276:immunology / Q000503:physiopathology; D013166:Spondylitis / Q000276:immunology; D013997:Time Factors
chemical_list: D015796:HLA-B27 Antigen